In particular, in the following, with motor craft it will be meant a craft provided with any propelling and/or manoeuvring means, even water jet propulsions.
It is known that the manoeuvre of multi-motor (or single orientable motor) crafts in restricted spaces entails difficulties due above all to the multiplicity of commands and to their poor intuitiveness which may put the pilot, especially if not skilled, to serious trouble. In any case, even skilled pilots may encounter great difficulties in manoeuvring crafts in particular conditions, such as for instance adverse meteorological conditions wherein not much foreseeable external disturbances may further hamper the manoeuvre.
In order to overcome these problems, some control systems for crafts have been developed based on the use of a control stick lever (or joystick) or other intuitive control means.
U.S. Pat. No. 6,511,354 discloses a single control lever with two degrees of freedom. The first degree of freedom allows the lever to be tilted backwards and forwards. The reversing gear hand lever command is associated with this movement which command simultaneously and in the same way acts upon both stern motors with which the craft is provided. The second degree of freedom allows the lever to be rotated on its axis. An unbalance between the motors is associated to this command so as to promote rotation of the craft according to the direction of rotation of the lever. System operation is controlled by an electronic gearcase controlled by the lever mechanism controlling the two main stern motors, and possibly a bow manoeuvre propeller, arranged according to the transverse axis. In addition, the lever system may operate four switches, two of which are arranged according to a transverse direction, whereas the other two are arranged according to a fore-and-aft direction, so that a forwards-backwards or rightwards-leftwards movement of the lever selectively makes them trip: this system preferably controls a specific, supplementary propelling system for low speed manoeuvre.
U.S. Pat. No. 6,234,853 discloses a control system for crafts substantially based on a joystick controlling an electronic gearcase controlling the main motors and possibly the manoeuvre motors. In order to make the main manoeuvres, this system requires that the motors may orientate their thrust, and therefore the system is applicable only to crafts provided with stern motors or outboard motors. Also, in order to reach its whole operation, the system requires the capacity of manoeuvring the orientation of the two motors independently of one another.
However, the solutions proposed so far suffer from some drawbacks.
First of all, in the proposed systems, a direct and one-to-one relationship exists between the movements of the intuitive control, such as the joystick, and the direction and speed setting of the propelling and manoeuvring means, leaves to the pilot the task of compensating the errors of the control system due to the effects of the craft dynamics, in particular due to the effects of inertia and hull.
Moreover, such systems do not take account of the effects due to external disturbances, such as wind and current.
Still, in the existing systems, the problem of the system calibration depending on the features of the craft and of the motors is not considered.
Furthermore, many of the present manoeuvre aid systems require specific propelling means, which make the systems very complex and expensive and not easily retrofit applicable to already existing crafts.
Finally, such systems do not include the function of maintaining a position and/or an attitude and/or an advance direction which are fixed and selectable by the pilot.